Glycemic Index, Glycemic Load, and Prevalence of the Metabolic Syndrome in the Cooper Center Longitudinal Study

Objective Previous research examining the relationships among glycemic index, glycemic load, and the metabolic syndrome has resulted in inconsistent findings. The objective of this study was to examine whether glycemic index and glycemic load are associated with prevalent metabolic syndrome and its components after adjustment for cardiorespiratory fitness, an objective measure of physical activity habitus. Design Cross-sectional study. Subjects/setting Women (n=1,775) and men (n=9,137) who completed a comprehensive medical examination between October 1987 and March 1999, including maximal treadmill exercise test and 3-day dietary records at the Cooper Clinic, Dallas, TX. Main outcome measures Metabolic syndrome and its components, defined by the revised Adult Treatment Panel III criteria. Statistical analysis Multiple logistic regression models were used to estimate sex-specific odds ratios and 95% confidence intervals to evaluate the associations among glycemic index, glycemic load, and prevalent metabolic syndrome and its components, while adjusting for potential confounding variables. Results Prevalence of metabolic syndrome was 24% in men and 9% in women. A positive association across quintiles of glycemic index and metabolic syndrome, elevated triglycerides, and low high-density lipoprotein cholesterol (HDL-C) in men was observed in the fully adjusted model (P for trend<0.05). In women, glycemic index was positively associated with large waist girth, low HDL-C, and elevated triglycerides (P for trend<0.05 for all) after multivariate adjustment including cardiorespiratory fitness. Glycemic load was positively associated with elevated triglycerides and low HDL-C (P for trend<0.0001) and inversely associated with prevalence of large waist girth and elevated glucose (P for trend<0.0001) in men. Among women, glycemic load was positively associated with elevated triglycerides (P for trend=0.04) and low HDL-C (P for trend<0.0001) in the multivariate model including cardiorespiratory fitness. Conclusions A lifestyle that includes a low glycemic diet can improve metabolic risk profiles in men and women. Prospective studies examining glycemic index, glycemic load, and metabolic syndrome that control for cardiorespiratory fitness are needed. J Am Diet Assoc. 2010;110:1820-1829.